Two-stage-FFT-based digital broadband high-precision frequency measuring method and system

Abstract

The invention provides a two-stage-FFT-based digital broadband high-precision frequency measuring method and system. Zero-intermediate-frequency AD sampling is carried out on a signal or after sampling, down-conversion is carried out to form a zero-intermediate frequency signal and the processed signal is sent to a signal processing module; the signal processing module receives an original signal,the signal is divided into two paths, and one path of signal is used as original data for storage; the other part of data are used for FFT; modulo calculation is carried out on the result after FFT and over-threshold detection is carried out to detect an over-threshold signal; digital down conversion is carried out on the stored original signal by using the signal obtained by over-threshold detection as guidance, so that the processed signal is transformed to be at a zero-intermediate frequency position; filter extraction is carried out on the signal after frequency conversion; baseband dataafter filter extraction are sent to an upper computer; and the upper computer carries out large-point-number FFT on the baseband data to obtain a high-precision frequency result. Therefore, the high frequency measurement accuracy is kept at a high sampling rate under the circumstance of limited hardware resources.

Description

Technical field [0001] The invention relates to a digital broadband high-precision frequency measurement method and system based on two-stage FFT, and relates to the technical field of electromagnetic signal detection. Background technique [0002] The electromagnetic signal frequency detection system is an important part of the reconnaissance receiver. In terms of receiver principle, frequency measurement methods are mainly divided into analog frequency measurement and digital frequency measurement. Analog frequency measurement mainly measures frequency by detecting time-domain signals. This method has a simple structure, but the frequency resolution, measurement accuracy and sensitivity are poor. Digital frequency measurement methods mainly include time-frequency analysis (wavelet transform), discrete Fourier transform (DFT) and phase measurement methods. Although the time-frequency analysis method can analyze the subtle characteristics of the pulse signal, the algorithm is m...

AI Technical Summary

Problems solved by technology

However, if there is more data, the amount of calculation will increase, which will affect the calculation speed and increase the calculation time.

In engineering, we often require wider instantaneous bandwidth and smaller frequency resolution. Due to hardware limitations, the actual FFT length cannot be infinitely long. Therefore, when the instantaneous bandwidth is wide enough, the frequency resolution cannot be guaranteed to be small enough at the same time.

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